This invention relates generally to methods for inhibiting the discoloration of physiologically injured fruits and vegetables, and relates more particularly to methods for inhibiting the formation of white blush discoloration on freshly processed carrots.
When many fruits (i.e., apples, pears, peaches, avocados, and bananas) and vegetables (i.e., beans, potatoes, mushrooms and many root crops) are bruised, or are cut, peeled, or processed in any other way that causes tissue injury, a black or brown discoloration appears at the situs of the tissue injury within a few minutes due to enzymes of the melanosis reaction. This discoloration problem has been the subject of much study, because of its obvious economic importance to the food processing industry.
Unlike the fruits and vegetables discussed above, carrots do not develop black or brown discolorations after suffering tissue injuries due to enzymes of the melanosis reaction. Consequently, the carrot is an ideal vegetable to process shortly after harvest into a form that is ready for consumption. Of the estimated 3 billion pounds of carrots that are marketed in the United States each year, approximately 20% are peeled soon after harvest to be sold as fresh miniature carrots, carrot sticks, carrot coins, carrot shreds, and other forms of fresh processed carrots.
Whole, unprocessed carrots may be stored under refrigeration for many weeks without significantly deteriorating. However, freshly processed carrots that have been in refrigerated storage for just a few days begin to develop a whitish, chalk-like appearance on their abraded surfaces. In the carrot processing industry, this whitish, chalk-like appearance is known as "white blush."
The rate at which white blush appears on processed carrots is a function of the physiological condition of the whole carrots prior to processing, the degree of abrasiveness that was present in the processing, the chemical treatments that were applied to the carrots, if any, and the humidity levels and the temperatures at which the carrots have been stored. For example, variations in the physiology of the whole, unprocessed carrots caused by different degrees of environmental stresses during the growing period, such as heat stress and drought stress, will result in variations in the onset of white blush formation under given storage conditions. Carrots that were grown in poorly irrigated fields tend to form white blush discoloration more rapidly, than do processed carrots that were grown in well irrigated fields.
White blush discolorization is unsightly and unappetizing. As a result, consumers invariably associate white blush with distastefully old carrots, even though the taste and nutritional value of processed carrots are not affected by the appearance of white blush. This fact leads to significant commercial waste when processed carrots are pulled from the shelf due to the appearance of white blush even though taste and nutrition are not being effected.
To date, white blush has been controlled primarily by washing freshly processed carrots with chilled water, usually in a hydrocooler, followed by refrigeration and/or by packaging of the freshly processed carrots in specialized containers, including some that maintain modified atmospheres within the containers. Chlorine has also been added to the chilled water treatments for sanitation purposes, and primarily to control microbial bacteria growth on the processed carrots. However, depending upon the variables recited above, the onset of white blush may only be delayed for a few days when utilizing the methods of the prior art.